Page 324 - The Complete Rigger’s Apprentice

an utterly unnecessary redundancy (Why not have the mizzen of his evolutionary ketch Sundeer (Fig-
four uppers? Eight lowers?), and make tuning a ure 8-7). And there’s even a forestay and backstay,
bear, since just getting slack out of the backstays details more commonly associated with mainmasts.
can mean an overtightened jibstay. In addition, twin Modern details aside, this mizzen has a lot in
backstays on a ketch preclude flying a mizzen stay- common with the ones mentioned previously. Like
sail–a sail that is one of the bonuses of the ketch rig– them, it’s a place to hang a staysail for reaching
because you’d chafe the leech on the weather stay. power, makes for a lower center of effort than a
sloop of comparable sail area, and is part of a versa-
Sojourner Truth tile, easily handled sail plan. But there are two other
This beautiful Morgan Giles-designed ketch is important mizzen virtues that Sundeer in particular
plagued by a mizzenmast so limber it makes the one exemplifies. One, mentioned briefly at the beginning
on Jenny Ives look positively docile. of this essay, is the mizzen’s helpmate relationship
The lower shrouds attach high up (Figure with the main. Sloop proponents talk about a split
8-6), à la Concordia, but unlike the Concordia, the rig’s “inefficiency,” then usually go on to how having
spreaders for the upper shrouds are also up high, a mizzen means you have to buy a whole extra mast,
leaving a long unsupported panel to deck. Worse sails, and rigging. They admit only grudgingly that
yet, the bottom of the jumper stay attaches to the a ketch or yawl might be easier to handle or more
middle of that unsupported panel, encouraging it to versatile. And they never mention that the main on
buckle. Even so, these details would not be so much a ketch can be much smaller and cheaper than it
of a problem if the mast were simply stiffer. But it would be if it had to absorb the mizzen’s sail area.
isn’t, and being wooden, it can’t readily be stiffened, Nor do they take into account that the mizzen pro-
like aluminum, by the addition of an inner sleeve. longs the main’s life by reducing the intensity of the
It might have helped to relocate those spread- cyclic loading that contributes to metal fatigue. In
ers down below the lower shrouds, but instead this Sundeer the mizzen is over half the size of the main-
mast has been fitted with “X-spreaders,” four struts sail. This is a big mizzen (20 to 40 percent of main
affixed in the way of the jumper stay’s lower end, is more typical) for a ketch, but any appreciable
and braced against the four lower shrouds. It helps mizzen is a lot more than an extra mast stuck in the
some, but since the X’s don’t deflect the wires, the back of the boat.
mast can always move some before the struts stop it. The other mizzen virtue has to do with the rela-
It’s hard to be sure, but I would guess that some- tionship of the mizzen to the hull. By distributing
one, somewhere along the way, neglected to take stress over a wider area, a split rig is kinder to its
into account that this mast is deck-stepped. A keel- hull than a monomast. With many boats, this distri-
stepped mast, because it’s supported at deck level bution advantage is qualified, since mizzens, at least
by the partners, is stiffer than a deck-stepped mast on ketches, are often reefed or lowered first when the
of the same scantlings. In essence, the partners, act- wind comes up, leaving the main to deal with heavy
ing in concert with the step, form what engineers weather. This is sometimes done because main and
call a “couple.” Sojourner Truth’s mizzen acts like a staysails provide more drive than mizzen and stay-
deck-stepped mast designed to keel-stepped specs. sails, but most often it’s because, on most vessels,
For further details on calculating mast loads, see weather helm increases sharply with increased heel.
Chapter 5. Mizzens, being so far aft, only exacerbate weather
helm, so down they come. But this is a design flaw
Sundeer in hull, not sail. A balanced hull like Sundeer’s does
Yacht designer and world cruiser Steve Dashew not suffer hull-induced weather helm as it heels.
brings mizzens into the New Age. There’s a high-as- And on Sundeer, Dashew has gone a step fur-
pect, double-spreader, intentionally “bendy” rig on ther, intentionally matching hull and sail plan so

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